Particle separator



Dec. 23, 1969 P DE|NKEN ET AL 3,485,360

PART I CLE SEPARATOR Filed Aug. 11, 1967 United States Patent 3,485,360 PARTICLE SEPARATOR Herman P. Deinken, Los Alamos, Jack Hill, Espanola, and Donald L. Bell and John A. Zastrow, Los Alamos, N. Mex., assignors to the United States of America as represented by the United States Atomic Energy Commission Filed Aug. 11, 1967, Ser. No. 660,892 Int. Cl. B07b 13/10 US. Cl. 209-117 2 Claims ABSTRACT OF THE DISCLOSURE A particle separator comprising a horizontal plate, means for rotating said plate in a horizontal plane about a vertical axis, means for dropping particles on said plate, and vacuum means for picking up at least some of the particles from said plate is described.

The invention described herein was made in the course of, or under, a contract with the US. Atomic Energy Commission.

The particle separator is a device which is used to grade small particles according to their sphericity. The separator works on the principle that rolling friction for a spherical particle is less than sliding friction for an irregular particle of the same size. When a mixture of particles, some spherical and some irregular in shape, is fed from the hopper onto the plate which is rotating at a constant angular speed, the spherical particles quickly roll to the outside edge of the plate and fall into one of a series of troughs located around the perimeter of the plate. The irregular particles must slide over the surface of the rotating plate to reach the edge and fall into a trough. Such particles move more slowly toward the perimeter of the plate and thus either fall off at a position farther from the feed hopper or they remain on the plate and are removed by the vacuum pickup.

One can better understand how the particle separator works by examining the forces on a particle which is riding on the upper surface of the plate which is rotating at a constant angular speed. The centrifugal force on the particle is acting in a positive radial direction and its magnitude is mw r when m is the mass of the particle, w is the angular speed of the plate, and r is the radius of rotation of the particle. If the particle is moving on the plate in a positive radial direction, then an opposing force on the particle, or one which is acting in a negative radial direction, is that due to friction between the particle and the surface of the plate. This frictional force may be expressed as ;tmg where p. is the coefiicient of friction, m is the mass of the particle, and g the acceleration due to gravity. The net force F on a particle which is moving in a positive radial direction on the plate is:

F,,: mw rmg 1) One can also express F as F n= n where a is the acceleration on the particle. Substituting ma for E, in Equation 1 gives:

3,485,360 Patented Dec. 23, 1969 "ice where a and a are the respective accelerations on the sliding and rolling particles and ,u and ,u, are the sliding and rolling coefi'icients of friction for the particles. Since a is greater than ,u, for particles of the same size moving over the same fiat surface, then one sees by comparing Equations 4 and 5 that the acceleration on the rolling particle is greater than that on the sliding particle. Since the mixture of particles is fed onto the plate with the same initial velocity and since the spherical particles have the larger acceleration at all radii on the plate, then it follows that the spheres will reach the edge of the plate before the irregular particles.

It is therefore an object of this invention to provide a device and method for a separation of particles, especially irregular shaped particles from spherical shaped ones.

Other objects of this invention will be apparent from the following description of the preferred embodiment and with reference to the accompanying drawing of which:

The figure is a partial, sectional view of the particle separator.

Referring now to the figure, there is shown a variable speed motor 1 which is mechanically connected to a drive shaft 2 which in turn rotates plate 3. The rotational speed depends on the mass, shape, and surface finish of the particles which are to be separated. The particles are fed into hopper means 8 which is supported by support structure means 5, said particles emerging onto the plate from a restricted spout 6 consisting of a small aperture which allows a small stream of particles to be deposited on the plate, said particles 7 thereupon being rotated in a clockwise .direction causing the more spherical shaped ones to be deposited in the trough 4 which is concentrically located around the perimeter of plate 3, while the irregular shaped particles are picked up through vacuum uptake 10 and vacuum line 9, and thus removed from the plate 3.

The particle separator has been used to grade steel, glass, boron, and boron carbide particles of sizes from 0.002 to 0.040 inch in diameter. One should be able to use the particle separator over an even wider range of particle sizes and for any material which can be fabricated into spheres. The rotational speed of the plate on the machine in current use may be adjusted continuously from zero to rpm. The speed of the plate for efiicient particle separation is determined by the properties of the particles being graded.

What is claimed is:

1. A particle separator for separating spherical particles from nonspherical particles comprising a circular, fiat, horizontal plate without surface obstructions, means for rotating said plate in a horizontal plane about a vertical axis, means for dropping particles on said plate, and pickup means located adjacent to the upper surface of 3 said plate for picking up the particles that remain on said plate after the plate has rotated more than two hundred seventy degrees.

2. The particle separator of claim 1 wherein the pickup means is a vacuum pickup located adjacent to the upper surface of said plate for picking up the particles that remain on said plate, a vacuum line connected to said vacuum pickup and a vacuum source connected to said vacuum line.

4 References Cited UNITED STATES PATENTS M.- HENSON WOOD, JR., Primary Examiner RICHARD A. SCHACHER, Assistant Examiner 

